Inoculation Using Bacteria Covered Silicone Tubes Helps Scientists Research Chronic Infections

Inoculation Using Bacteria Covered Silicone Tubes Helps Scientists Research Chronic Infections

New scientific method unmasks chronic infections

Bacteriology

With the aid of tiny silicon tubes and one of Europe’s most sophisticated centres for microscopy, scientists have been able for the first time to observe directly bacteria in chronic infections. Researchers can now see precisely how bacteria and the immune system interact in living tissue. This opens the potential for developing new medicine to fight resistant bacteria. The results have recently been published in the scientific journal Infection and Immunity.

Associate Professor Thomas Bjarnsholt explains the new method in the video above. Production: Henrik Prætorius, Experimentarium. Credits: University of Copenhagen.

Chronic infections are a large and growing problem throughout the developed world, and intensive research is being conducted in ways to combat the recalcitrant bacteria. When bacteria aggregate into so-called biofilm, they become resistant to antibiotics. Until now scientists have only been able to speculate about what happens when bacteria overpower the immune system during a chronic infection.

In close collaboration between various specialist fields, Danish scientists have now developed a method that gives a precise picture of how the immune system works. Using 5 mm silicone tubes, scientists created a model system that allows them to look closely at how the immune system and bacteria interact in isolation:

Using 5 mm silocone tubes enables the researcher to make a cross section of chronic infections.

Using 5 mm silocone tubes enables the

researcher to make a cross section of chronic

infections.

“Although we have always suspected that to cause a chronic infection, bacteria knock out the immune system’s white blood cells, the new method allows us to see precisely what happens. Instead of looking down on the bacterial surface, we can examine a section to see the interaction directly and follow how the bacteria react to white blood cells and to antibiotics. That enables us to understand the basic processes behind chronic infections,” explains Associate Professor Thomas Bjarnsholt, University of Copenhagen.

PhD student Maria Alhede adds:

“The new method allows us to investigate which compounds the bacteria are secreting while overpowering the white blood cells. Conversely, we can also see what happens when the immune system works. The white blood cells make DNA traps that capture the bacteria, but that used to be only a guess,” relates Maria Alhede, Department for International Health, Immunology and Microbiology.

Scientists follow the effect of drugs in the organism

The Core Facility for Integrated Microscopy at the Department of Biomedical Sciences has some of Europe’s most sophisticated microscopes for conducting health research. By combining light microscopy and electron microscopy, scientists can show visually exactly what happens in the body when biofilm bacteria meet the immune system or are treated with antibiotics. The method also makes it possible to investigate what processes are activated when scientists test new medicine. Many different types of patients will benefit from the discoveries.

[Chronic infections are a common complication when patients receive an implant e.g. an articficial knee.]

Chronic infections are a common complication when

patients receive an implant e.g. an articficial knee.

“Chronic infections most often arise when we introduce foreign objects into the body, such as catheters and implants like artificial hips and knees. But chronic bacterial infections also plague many children with middle-ear infections, as well as diabetics, who run a great risk of developing chronic sores on legs and feet. For patients with cystic fibrosis, the chronic pneumonia caused by the aggressive Pseudomonas bacteria is directly life-threatening. Now we have the opportunity to see the exact mechanism of a drug,” explains Professor Niels Højby from Rigshospitalet.

Scientists hope that many people will eventually benefit from the method and that it can contribute knowledge to other areas, such as immunology, because the results were achieved in the interface between various research areas:

“We asked the right questions of the right experiments many times and over a long period. Success is due to collaboration across the lines of research groups and our exploitation of the finely meshed network of expertise,” explains Associate Professor Thomas Bjarnsholt.

Chronic infections with Pseudomonas aeruginosa persist because the bacterium forms biofilms that are tolerant to antibiotic treatment and the host immune response. Scanning electron microscopy and confocal laser scanning microscopy were used to visualize biofilm development in vivo following intraperitoneal inoculation of mice with bacteria growing on hollow silicone tubes, as well as to examine the interaction between these bacteria and the host innate immune response. Wild-type P. aeruginosa developed biofilms within 1 day that trapped and caused visible cavities in polymorphonuclear leukocytes (PMNs). In contrast, the number of cells of a P. aeruginosa rhlA mutant that cannot produce rhamnolipids was significantly reduced on the implants by day 1, and the bacteria were actively phagocytosed by infiltrating PMNs. In addition, we identified extracellular wire-like structures around the bacteria and PMNs, which we found to consist of DNA and other polymers. Here we present a novel method to study a pathogen-host interaction in detail. The data presented provide the first direct, high-resolution visualization of the failure of PMNs to protect against bacterial biofilms.

Disease causing bacteria often forms into clusters that are protected by biofilms from the body’s immune system. These biofilms have been a major topic of study in the fight against infectious diseases, but it’s been hard to come up with methods that help isolate the interaction between the biofilms and the immune system for prying microscopes to look at.

Researchers at the University of Copenhagen have reported in journal Infection and Immunity of a way of using injected hollow silicone tubes with bacteria grown on them, and scanning electron microscopy along with confocal laser scanning microscopy, to really see what the immune system is up to when it encounters biofilms.

From the study abstract:

Wild-type P. aeruginosa developed biofilms within 1 day that trapped and caused visible cavities in polymorphonuclear leukocytes (PMNs). In contrast, the number of cells of a P. aeruginosa rhlA mutant that cannot produce rhamnolipids was significantly reduced on the implants by day 1, and the bacteria were actively phagocytosed by infiltrating PMNs. In addition, we identified extracellular wire-like structures around the bacteria and PMNs, which we found to consist of DNA and other polymers. Here we present a novel method to study a pathogen-host interaction in detail. The data presented provide the first direct, high-resolution visualization of the failure of PMNs to protect against bacterial biofilms.

[video src="http://video.ku.dk/4959050/6657224/19717668cc18e388dfa68f0a1c68a612/video_webm_360p/share/new-method-unmasks-chronic-video.webm" /]

source : http://news.ku.dk/all_news/2012/2012.8/new_scientific_method_unmasks_chronic_infections/

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